(a) Field of the Invention:
The present invention relates to a television camera, and more particularly it relates to an improvement of the television camera which can be used suitably with an endoscope or like devices.
(b) Description of the Prior Art:
For example, endoscopes include a non-flexible endoscope which uses a relay lens system serving as the optical system intended to lead, to an ocular unit or eyepiece, the image formed by the objective lens, and a fiberscope using an image guide fiber bundle. Arrangement is provided so that, in case an image obtained by such an endoscope as mentioned above is to be observed through a TV monitor, an image pickup is performed by a television camera which is attached to the eyepiece of the endoscope. In such a case, however, there have to be prepared on hand various types of adapters for selective use with non-flexible endoscopes and fiberscopes, or for respective types of fiberscopes for replacement to be suitable for respective fiberscopes, which have been quite troublesome to operate. Also, in television cameras in general, the arrangement of picture elements of an image pickup device, scanning lines, color separation stripe filter, etc. form regular lattices, so that in case an object to be photographed contains regular lattice portions, there develops moire on the TV monitor screen due to interference, so that arrangement has been provided usually to provide an optical low-pass filter between the photographic lens and the image-forming surface to thereby prevent the development of moire. It should be noted here, however, that this low-pass filter is selected so as to be effective for general photography by the television camera, i.e. for photography of landscapes, persons and the like, so that in case a photography is performed by attaching a TV camera to a fiberscope having a structure that the core portion of the image guide fiber bundle is of a regular arrangment, there has been the inconvenience that, because the exit end face of the image guide fiber bundle has a regularity, it has not been possible to sufficiently prevent the occurrence of moire phenomenon.
For the reasons mentioned above, it has been the practice in the past to use an adapter which has, incorporated therein, only a photographic lens for such an apparatus as a non-flexible endoscope, and also to use, in case of a fiberscope, an adapter in which are incorporated a photographic lens and a low-pass filter intended to eliminate moire. Besides, in view of the fact that different moires apt to develop depending on the size of the respective constituent fibers of the image guide fiber bundle or on the type of the ocular, there has to be prepared, on hand, adapters in which are incorporated different low-pass filters, respectively, for each type of fiberscopes. Thus, there has been the problem that the prior art devices are very poor and troublesome inoperability.
Also, if it is made possible to switch one filter to another to meet various circumstances of use not only in endoscopes but also in television cameras and in electronic still-cameras in general, it is possible to photograph an object always with a highest degree of resolution, and thus this would be convenient.